DaCross

Abstracts of clinical and scientific research articles


by David Crossley and associates

# indicates abstracts of articles published in refereed journals.
* indicates a paper presented at a scientific meeting.

TOOTH ENAMEL THICKNESS IN THE MATURE DENTITION OF DOMESTIC DOGS AND CATS - A PRELIMINARY STUDY
David A. Crossley

Summary:

    The thickness of the enamel of dogs and cats was measured in 194 teeth. The enamel was found to be thinner than that of human teeth, varying in thickness from 0.1 mm-1 mm. The "enamel bulge" coronal to the cemento-enamel junction does not consist of a thickened area of enamel.

Journal of Veterinary Dentistry, 12(3): 111-113, 1995

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CLINICAL ASPECTS OF LAGOMORPH DENTAL ANATOMY : THE RABBIT (ORYCTOLAGUS CUNICULUS)
David A. Crossley

Summary:

    The lagomorphs most commonly encountered as pets are rabbits. There are many breeds of domestic rabbit, varying from dwarf varieties with an adult weight of under one kilogram to giants weighing 10 kg. This article provides a working knowledge of the dental anatomy and physiology of rabbits so that veterinarians can interpret clinical and radiographic findings when investigating rabbits with suspected dental disease.

Journal of Veterinary Dentistry, 12(4): 137-140, 1995

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CLINICAL ASPECTS OF RODENT DENTAL ANATOMY
David A. Crossley

Summary:

    The order Rodentia is vast, encompassing a large number of species with significant anatomical variations developed during natural adaptation to differing habitats. Many veterinarians have little knowledge of the a natomy of species other than the commoner domestic large herbivores and small carnivores. Clinicians require a basic knowledge of the relevant anatomy of species they are likely to be asked to treat. This article provides sufficient working knowledge of the oral and dental anatomy of those rodents commonly kept as pets to enable veterinarians to interpret clinical and radiographic findings when investigating suspected dental disease.

Journal of Veterinary Dentistry, 12(4): 131-136, 1995

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OCULAR AND NASAL SIGNS IN RABBITS WITH DENTAL DISEASE:
A RADIOGRAPHIC STUDY
David A. Crossley

Introduction:

    Rabbits may show various ocular and nasal signs including epiphora, conjunctival or nasal discharge, conjunctivitis and proptosis as a result of dental disease. Radiography has proved useful when investigating such cases.

Method:

    The anatomy of the dentition, orbit and lacrimal drainage system of normal animals and those with ocular signs were studied using conventional and contrast radiography.

Results:

    The osseous components of the orbit and the dental anatomy, can be clearly demonstrated by radiography. Some soft tissues can also be assessed. Dental pathology can often be detected radiographically before it is apparent on physical examination. Evidence of dental lesions affecting the lacrimal drainage system and the orbit are common in rabbits with ocular and nasal signs.

Discussion:

    Rabbits have a full set of teeth which grow continuously throughout life. If there is any interference with eruption of these teeth, 'root extension' occurs. As a result the tooth roots may invade the orbit displacing the eye or preventing its retraction into the orbit. Endodontic disease or extension of periodontal lesions along tooth roots can result in periapical abscessation. When the cheek teeth are involved the result may be a retrobulbar abscess. If the incisor teeth are affected the naso-lacrimal duct may become involved, with obstruction of normal tear drainage or discharge of pus via the duct to either or both the eye and nose.

Conclusions:

    Radiographic investigation of ocular disease is worthwhile in rabbits.

Clinical research abstract, Proceedings,
British Small Animal Veterinary Association Congress 1996

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EXTRACTION OF RABBIT INCISOR TEETH!
David A. Crossley

Summary:

    Incisor malocclusion is a frequently seen problem in domestic rabbits. It is less frequently encountered in rodents. Maloccluded incisor teeth in rabbits and rodents are non-functional and hinder rather than assist prehension of food. Overgrowth of the incisors also interferes with jaw movement preventing adequate mastication of any food entering the mouth. This leads to abnormal wear patterns in the cheek teeth further exascerbating the situation.

    The customary treatment has been to trim the affected teeth at frequent intervals to prevent the problems associated with tooth overgrowth. A more satisfactory solution in cases of persistent or recurrent incisor malocclusion is the extraction of the offending incisor teeth. This procedure and its potential complications are described.

European Veterinary Dental Society Forum, 1993, No.4

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CARIES AND ODONTOCLASTIC RESORPTIVE LESIONS IN A CHINCHILLA (Chinchilla lanigera)
Crossley DA, Dubielzig RR, Benson KG

Summary:

    It is well recognised that domesticated chinchillas (Chinchilla lanigera) suffer from a range of dental problems, the most frequent of which is the result of reduced and uneven coronal wear of the premolar and molar (cheek) teeth with resultant root elongation and secondary malocclusion (Crossley 1995 + 1997). Although rarely detected clinically, destruction of dental hard tissue can often be recognised at post-mortem and in prepared skulls. This paper reports the histological confirmation of caries and odontoclastic resorptive lesions in a chinchilla.

Veterinary Record, 1997, 141:13 337-9

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USE OF COMPUTED TOMOGRAPHY TO INVESTIGATE CHEEK TOOTH ABNORMALITIES IN CHINCHILLAS (Chinchilla lanigera)
Crossley DA, Jackson A, Yates J, Boydell IP

Abstract:

    Computerised tomographic scanning was used to investigate tooth structure in chinchillas (Chinchilla lanigera), both cheek tooth crown and root abnormalities being common in this species. This paper describes a common form of dental disease affecting species with continuously growing teeth, with particular reference to the chinchilla, and confirms the potential role of computed tomography (CT) in its early diagnosis. CT imaging is compared with previously available methods of investigation which frequently fail to detect early pathological changes.

Journal of Small Animal Practice, 1998, 39:8 385-9

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ANATOMY OF THE CHINCHILLA (Chinchilla lanigera) LACRIMAL DRAINAGE SYSTEM
Crossley DA, Roxburgh G,

Introduction:

    Chinchillas (Chinchilla lanigera) are becoming popular as pets. A common clinical sign seen in chinchillas is "wet eyes" due to lacrimal overflow.

Aim:

    To investigate the normal anatomy of the lacrimal drainage system in the chinchilla to enable further study into the causes of lacrimal overflow.

Method:

    Clinical examination, radiography and CT scanning, plus anatomical dissection, histological examination and photography of available post-mortem specimens.

Results:

    There are two lacrimal punctae at the medial canthus of each eye. After a short distance these drain into the single lacrimal duct that enters a bony lacrimal canal. The lacrimal duct is lined by epithelial cells including a proportion of mucus secreting goblet cells. The bony lacrimal canal passes diagonally rostro-ventrally past the root apices of the more rostral cheek teeth, continues towards the root apex of the incisor tooth. The lacrimal canal narrows and passes medial to the incisor then alters direction, continuing a short distance rostro-dorsally with the lacrimal duct continuing several millimetres to enter the nasal chamber just inside the nares.

Conclusions:

    Lacrimal drainage in chinchillas appears similar to that in other rodents and the rabbit. The point most likely to become obstructed appears to be adjacent to the incisor tooth root, as occurs in rabbits. A further study is investigating the site of obstruction in animals with "wet eyes".

Clinical research abstract, Proceedings,
British Small Animal Veterinary Association Congress 1999

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THE SITE OF OBSTRUCTION OF THE LACRIMAL DRAINAGE SYSTEM IN CHINCHILLAS (Chinchilla lanigera) WITH "wet eyes"
Crossley DA, Roxburgh G

Introduction:

    A common clinical problem seen in chinchillas (Chinchilla lanigera) is "wet eyes" due to lacrimal overflow.

Aim:

    To investigate the site or sites of obstruction of the lacrimal drainage system in chinchillas showing signs of lacrimal overflow.

Method:

    Radiography, CT scanning, anatomical dissection, and histological examination of affected animals. signs of lacrimal overflow.

Results:

    The main site of obstruction of lacrimal drainage is in the descending portion of the lacrimal canal between the orbit and the incisor tooth root apex. Bony remodelling around elongating maxillary premolar and first two molar tooth roots intrudes into the lacrimal canal compressing and sometimes occluding or even obliterating the lacrimal canal and duct. No evidence has been found for obstruction adjacent to the incisor root apices in the specimens examined so far.

Discussion:

    Lacrimal drainage in healthy chinchillas is similar to that in other rodents. This species is adapted to a highly abrasive herbivorous diet, having continuously growing cheek teeth (in addition to the continuously growing incisors). When these teeth are not worn adequately, i.e. when domestic animals are fed commercial diets, the teeth continue to elongate. Eventually occlusal pressure prevents eruption, so the roots intrude inducing remodelling of adjacent tissue including the lacrimal canal.

Conclusions:

    Chinchillas should be fed a herbivorous diet which requires prolonged chewing in order to wear the teeth adequately.

Clinical research abstract, Proceedings,
British Small Animal Veterinary Association Congress 1999

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INCISOR TOOTH RE-GROWTH FOLLOWING COMPLETE EXTRACTION IN A RABBIT
Steenkamp G, Crossley DA

Summary:

    Incisor extraction in rabbits has become a standard procedure in veterinary practise. This is a very technique sensitive operation with many potential complications, particularly when the operator is inexperienced. In this case report we describe a complication, i.e. incisor re-growth, that occurs particularly when the operator is highly competent at using atraumatic technique. Suggestions are made for the controlled disruption of the germinal tissue at the root apex in order to prevent tooth re-growth.

Veterinary Record 1999, 145, 585-586

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DENTAL DISEASE IN CHINCHILLAS IN THE UK
David A. Crossley

Abstract:

    Dental abnormalities are common in chinchillas, however, knowledge of the nature and relative incidence of the lesions responsible for clinical signs is incomplete. Animals, radiographs and/or prepared specimens were examined to gain further knowledge regarding dental anatomy and dental disease in the UK chinchilla population.

    Thirty five percent of the apparently healthy chinchillas examined had dental abnormalities detectable on routine examination. The range and relative incidence of different dental abnormalities encountered in these and clinically affected animals are presented. Whilst malocclusion was a common finding, in all but one case this was secondary to crown elongation or absence of opposing teeth, not a primary skeletal problem.

    Clinical signs commonly attributed to malocclusion, such as ventral mandibular swelling, weight loss, dysphagia, altered chewing pattern and changed food preferences, are not specific to malocclusion. They are seen associated with tooth root elongation, spike formation on the sides of the occlusal surfaces and advanced periodontal lesions. Caries and odontoclastic resorptive lesions rarely cause obvious clinical signs but were identified regularly. Congenital absence of cheek teeth, true skeletal malocclusion and pathological loss of incisor teeth all resulted in significant clinical signs but were rarely seen.

    Lack of dietary abrasion and stress are probably the main aetiological factors for the most prevalent dental problem, cheek tooth elongation. Combination of provision of a diet matching that eaten by wild animals and reducing stress levels of captive chinchillas should reduce the incidence of dental disease in this species.

Journal of Small Animal Practice 2001, 42:1, 12-19

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SKULL SIZE AND CHEEK TOOTH LENGTHS IN WILD AND CAPTIVE CHINCHILLA POPULATIONS
David A. Crossley and Maria del Mar Miguélez

Summary:

    Chinchillas are herbivorous rodents with teeth that all grow continuously. In captivity they are commonly affected by dental disease. Since the range of dental disease occurring in wild chinchillas is unknown, the dentition of museum specimens originally obtained from the wild was assessed and compared with specimens prepared from captive bred animals.

    Skulls from wild-caught chinchillas showed minimal evidence of dental disease and the teeth were all short, cheek tooth lengths averaging 5.9 mm. Cheek tooth lengths in zoo specimens (average 6.6 mm), clinically normal (average 7.4 mm) and captive bred animals with dental disease (average 10 mm) were significantly elongated by comparison (p < 0.0001). Captive bred specimens showed a wide range of tooth related lesions.

    These results suggest that some aspect of captivity is responsible for the development of dental disease in chinchillas. It is suggested that the diet (its physical form and composition) is the main etiological factor, and that provision of a diet closely matching that of wild chinchillas should significantly reduce the incidence of dental disease in captive chinchillas.

Archives of Oral Biology 2001, 46:10, 919-928

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This page was last updated on24th April, 2004.